Bacterial wilt disease (damping-off) is a disease infectious to not less than 200 species of plants including solanaceous plants, and causes death of the plants, leading to serious damage to agriculture. In cases where progression of the disease occurs rapidly, the plant dies while the plant remains green, and it is said that the name was given because of such a fact. The disease has a characteristic that, when the stem of a plant suffering from bacterial wilt disease is cut at a position near the soil and immersed in water, milky mucus (bacterial ooze) exudes from the stem.
As main pesticides for bacterial wilt disease, chloropicrin and methyl bromide have been proposed. However, both chloropicrin and methyl bromide are dangerous drugs. Furthermore, methyl bromide is an ozone depleting substance, and use of methyl bromide has been banned since 2005. In general, bacterial wilt disease occurs in relatively warm regions, but the trend of global warming has accelerated spreading of the wilt bacterium and a decline in production of crops thereby, already causing loss of about 9.5 trillion yens per year in the world.
As described above, bacterial wilt disease occurs in relatively warm regions. However, wilt of potato caused by a cold-adapted bacterial wilt disease strain, race 3 biovar 2 phylotype II has already become a major threat to the United States, and it is said that spreading of the strain to Japan is just a matter of time. Thus, alternative means for effectively preventing or controlling the wilt bacterium are being developed and studied in Japan and other countries.
For example, Patent Literature 1 describes a method for controlling soil-borne diseases in solanaceous plants. More specifically, the literature describes a method wherein living bacteria of the Pseudomonas solanacearum (current academic name, Ralstonia solanacearum; which corresponds to the wilt bacterium) strain M4S; and a bacteriophage that causes bacteriolysis of both of the bacterium and pathogenic Pseudomonas solanacearum; are immobilized, and the obtained immobilized substance is applied to the soil. Patent Literature 2 describes a method for controlling the wilt bacterium by spraying a bacteriophage itself that causes bacteriolysis of the wilt bacterium onto the plant or the soil. The literature also describes a method for improving soil by addition of the bacteriophage to the soil.
On the other hand, Patent Literature 3, and Non Patent Literature 1 and Non Patent Literature 3 describe details of bacteriophages that specifically infect the wilt bacterium. For example, the φRSM1-type filamentous phage, φRSM3-type filamentous phage and φRSS1-type filamentous phage, which do not cause bacteriolysis of the wilt bacterium, are described in detail.